Connectalias, connectcanonical Channel Options

From MsgServerDocWiki

Envelope address rewriting upon message dequeue (connectalias, connectcanonical)

The MTA normally rewrites addresses as it enqueues messages to its channel queues. No additional rewriting is done during message dequeue. This presents a potential problem when host names change while there are messages in the channel queues still addressed to the old name.

The connectalias option tells the MTA to simply deliver to whatever host is listed in the recipient address. This is the default. connectcanonical tells the MTA to compare the recipient envelope address domain with the channel host proper names, and if the domain name matches one of the channel's host proper names, then connect to the host name corresponding to that host proper name. For instance, if a channel is defined (in pmdf.cnf/imta.cnf format) as:

tcp_scanner smtp connectcanonical ...rest-of-keywords... 
SCANNER-DAEMON 
scanner1.domain.com  host1.domain.com 
scanner2.domain.com  host2.domain.com 

then an address of user@host1.domain.com that rewrites to the tcp_scanner channel will be routed out to the host scanner1.domain.com, rather than to host1.domain.com as would occur by default.

connectcanonicalshould only be used specifically to deal with problems with queued messages---it may have unintended effects on other message traffic.